The last week or so have seen a political and scientific debate raging around an that has been organised jointly by the and the . The plan is to sail to the Southern Ocean and "add some 20 tons of iron sulphate to a 186-square-mile patch of ocean about half way between Cape Horn and the Cape of Good Hope".

The idea is that this will promote rapid algal growth. As the algal population booms it will consume significant quantities of CO2. When the iron is depleted, the scientists hope that the algae will die and fall to the bottom of the ocean, taking the sequestered carbon with them in an essentially natural, if accelerated, process.

As the ocean already absorbs a large proportion of atmospheric CO2 as part of the natural carbon cycle, increasing the rate of absorption and sequestration would seem a sensible idea. The plan is not without risks however. Some scientists fear that ocean fertilisation could lead to blooms of the wrong type of algae, causing poisoning of large areas of the ocean. Alternatively, the algae could de-oxygenate the waters or even release methane or nitrous oxide (both of which are far more damaging greenhouse gases than carbon dioxide, pound for pound). The potential risks associated with ocean fertilisation are such that it is illegal (except for small scale research studies within coastal waters).

by Tim Flannery also talks about this topic and I'd recommend reading it to anyone interested in anthropogenic climate change.

Ocean fertilisation is just one example of several techniques that have been proposed, from the exotic (shooting aerosols into the atmosphere to increase the earth's albedo) to the mundane (reforestation). David Keith talks more about geo-engineering in this excellent .

My feeling is that the risks associated with geo-engineering are very great (potentially as bad as, or worse than current climate change predictions), and that they should be considered only as a last resort. I believe that the technologies and behaviours we need to adopt to avert catastrophic climate change are understood and achievable with international focus and concerted effort.

I believe we should be researching geo-engineering options only out of academic interest, and that if we get to the point at which geo-engineering is required, we will already be too late to avert disaster for humanity. We have proved that as a species, we are unable to preserve our environment in anything but the most rudimentary of fashions. Are we really to believe that we can engineer our environments on such a very much larger scale with any higher degree of success?